Feeding device



Feb. 13, 1951 2,541,616

J. D. SASSER FEEDING DEVICE Filed Sept. 5, 1943 5 SheetsSheet l WWW M38 Feb. 13, 1951 J, s ss 2,541,616

FEEDING DEVICE Filed Sept. 5, 1943 3 Sheets-Sheet 2 OOOOOQG ()OOOOOOOOO OQOO OOGO 51; will Feb. 13, 1951 J. D. SASSER 2,541,616

FEEDING DEVICE 3 Sheets-Sheet 5 Filed Sept. 3 1945 WMQM cross arm by reason of its threaded engagement with shaft 24. The construction is essentially self-locking and upon the deenergization of the motor, there is little if any tendency for it to be rotated in response to the load on the platform I5. Suitable electromagnetic brake means 32 connected in series with the motor armature are preferably provided within the motor and efiective upon the motor shaft for assuring that the shaft will be held stationary when the motor is deenergized, such brake assuring also substantially the same degree of overrun each time the platform is stopped regardless of the load which it carries and its direction of movement.

In order to .control the operation of the motor to provide for stopping its operation when the platform I approaches either end of its travel, limit switch means are provided for opening the circuit to the motor. Such means includes an upper limit switch 35 and lower limit switch 36, mounted adjacent each other on the frame I3. Push rods 3? and 38 extend downwardly from the respective switches and are guided at their lower parts in bracket 39 secured to the casing, each rod having its lower end projecting through the bracket as shown in Fig. 1. For actuating the rod 37 and hence the up limit switch 35, platform is provided with a finger 43 which projects rearwardly through a vertically extending elongated slot dl in panel I I. As the platform rises and reaches its upper limit, finger 40 engages and lifts rod 3'! to open the motor circuit at switch 35, preventing further lifting of the platform. For actuating the rod 38 and the down limit switch 36, a finger 42 is carried on cross arm 22, being located in such position that as the platform is lowered and cross arm 22 rises to the desired limiting position, the finger will engage rod 33 to open the motor circuit at switch 36, preventing further lowering of the platform. It will thus be seen that these limit switches operate independently to make it impossible for the motor to actuate the platform in a given direction beyond a certain position. However, it will also be seen that whenever one limit switch is open, the other will be closed, and thus the motor will be able to reverse and thus to move the platform in the opposite direction.

It will be observed that the weight of the unused part of the string of ammunition on the platform varies substantially as the string is used and the platform is lifted. In order to facilitate the operation of the lifting mechanism under such circumstances and to tend to equalize the load imposed upon the drive motor, counterbalancing cans are provided which is effective to counterbalance and compensate for the change in load on the platform. For this purpose a pair of spring assemblies are mounted in vertically extending tubes 45 which are fastened to the outside of the casing by suitable means including the brackets 39 on opposite sides of shaft 24. Each tube has a slot extending transversely therethrough through which the cross arm 22 extends. Each tube contains preferably a pair of springs which are arranged to telescope within each other in order to secure a greater range of travel. There is an upper spring ii to the lower end of which is fixed a tubular member 43 which projects up into the spring, forming a chamber for receiving the lower spring 49 and rod 50 located inwardly thereof and shorter in length than tube 48. The upper end 68a of the tube 48 is at least partially closed to form an abutment for spring 49. The lower end of the rod 59 and spring 49 are adapted to engage cross arm 22. Thus when the cross arm begins to move upwardly, spring 49 which is somewhat weaker than spring d'l is forced against the upper end of tubular member t8 and is progressively stressed until it is almost fully collapsed. At this time cross arm 22 will engage the lower end of spring d? which has not been lifted to any material extent by the initial movement as doscribed. Further upward travel of the cross arm will however now compress spring 47 while keeping spring :9 under the tension originally applied, thus providing for developing a counterbalan-cin force which is greater when the cross arm is raised and the platform i5 lowered, becoming progressively less as the platform rises and the weight of the ammunition remaining thereon becomes less. The motor operation is thus facilitated and the load made more uniform, making possible the use of a smaller sized motor than wou.d otherwisebe required.

Mounted on the upper end of the casing and supported on flange i3 is a feed table or tray shown at 55. The tray does not entirely close the upper end of the casing but is spaced from one end thereof to provide a passage through which the string of ammunition may be withdrawn. The tray comprises an upwardly inclined feed surface 56 below which there is positioned the guide roller 5? carried on cross pin 57a, the periphery of the roller being suitably shaped to correspond with the surface of the ammunition lengthwise thereof, and to provide for smooth and even support and feeding of the ammunition in the arcuate path shown in Fig. 4, as the string is withdrawn from the casing and fed forwardly over the inclined surface 56. The tray is formed with laterally extending guides 58 at either side thereof which confine endwise movement of the ammunition as it travels across the tray. At its forward end the tray is inclined downwardly as shown at 59 to provide for direct feed of the ammunition into the gun mechanism, the gun mechanism being utilized to draw the string of ammunition on to the feed table and into the gun itself.

The feed table is removably supported on the casing ill to provide for removal thereof for the purpose of replenishing the supply of ammunition on the platform. For this purpose the tray seats in a recess in flange I3 and is formed with downwardly extending arms 6% which are apertured to receive pin 62 at their lower ends. Pin 62 is adapted to extend through suitable openings provided in the upper edge of flange I3 to provide for locking the tray in the assembled position. Pin 57a similarly locks the tray in position, removal of the tray being possible only upon removal of both pin 5 1a and 52.

The ammunition is arranged in a continuous string by means of clips indicated at 65 which connect each shell with the next in the series,

permitting the swiveling of one shell freely with respect to adjacent shells. The ammunition is then piled on the platform in a series of layers,

' extending back and forth across the platform.

The upper end of the string is withdrawn from the remote or left-hand end of the casing and fed over guide roller 51 and the feed tray into position to be engaged by the gun mechanism, as previously described.

It is desired to provide for control of the lifting of the platform automatically and without requiring the attention of the operator, and to cause the platform to be raised from time to time as the ammunition is utilized, to maintain the top of the pile-on stack-at substantiallyrae In this way the" main body of the ammunition is supported without depending uniform level.

i come very substantial, resultingin a-tendency'to so increase the drag: of thestringrof -ammunition where the gun is required to lift'the entire string by itself that the operation ofthe-gunis seriously interfered with, beingsubstantialy slowed down or even temporarily halted. With the present arrangement however the gun-mechanismis required to perform only a relatively-small part of the lifting operation, namely; to drawthe upper end of the string comprisingthe upper one or two layers, and to lift onlythe limited dstance from those layers to the feed tray-and-into the gun mechanism. Furthermore theload thus imposed does not vary substantially-as th string is withdrawn, but remains substantiallyuniform throughout the entire firing-ofthe gunfrom the time that the stringisfirst fed to the gun until it is exhausted. As a result, the operation of the gun is made more definite-and certain, and its firing under even the most severe conditions which may be encountered as a result of maneuvering, is assured and made rapid and-uniform.

For the purpose of securing such control of the lifting of the platform, thetray'55 carries a feeler device for sensing the level o-f the upper layer of the ammunition; This'feeler"device-comprises a shoe which has a forwardly projecting toe portion H adapted to-ride upon the upper level of the string of ammunition: This shoe is located adjacent the side of i the casing opposite that through which the string-is -fed, the-relationship being shown generally-in Fig: 4. The shoe is carried by a shaft 72 which is 'guided'for vertical movement ina sleeve 13 supported on-theunderside of tray 55 and is spring urgeddownwardly against the upper surface of the ammunition by spring 12a. Thesleeve is-formed-with a cut-out section 14 and shaft 12 is also notched out, thereby forming upper and lower surfaces for engagement respectively with a'nose piece 'l5'whichextends outwardly'intothis notched-out rart'for' the purpose of operating toggle switch 11 of which it forms-a part; The switch is carried on a bracket 18 supported from the side-of the tray and is of such character-that-it occupies either the up position shown-in'Fig; 4-in which it is'open,

ora down position in whicnit'isclosedj Theswitch is moved from oneposition to the other under the actionof the'nose-piece15'engaging the end of the switch arm to cause it 'to'move with a-snap action to one position or the other depending upon whether itis engaged by the upper or lower surface of the notch; A guard 80 is provided on the trayto enclose the switch and its operating mechanismin order to prevent possibility of the string of ammunitioncoming in contact therewith in the event 'of the aircraft turning over, for example: Guard'fill as well as the" switch bracket'lB- are oifset-as sh'owm at their portions tothe left ofandabove th toe 1 I mak ing it possibleforthe ammunition" to be lifted" anemia disconnecting anyof the wiring; and as readily replaced: For this purpose; the tray'is' provided with'a pair-of spring contacts 82 on oneside, below the level of surface 56;, with suitable wiring. extending from the contacts to the switch 11. Stationary contacts 84 are provided on'-;the upperend'ofthe casingfor engaging'the'resp'ective contacts 82' when the tray is'loweredto itsioperative' position, thus providing a quickly detachable connection to the feeler switch. No changes needibe f made in" the switch or. its wiring as carried on the tray however since this remains asa permanently connected'unit'.

In order to facilitate. access to the interiorof thecasing during'loadin'g'for example; a front panel off'the casing is provided with a removable section 9E!" which upon removal, provides" access totth'e entire interior. andis adapted'to seat within inwardly'project in place by. a cross bar 92the lower sideof which overlies the section to retain it in place.' Crossbar 52 isfastened inplace to hold'sectijon' 99 by'means' of a pair of wing nuts 93. which arev loosened to; allow thello'arto lift'up; at its lower side sufficiently for the panel section .90 to clear the same; the bar 92"havingelongatedslots 94 (Fig. 3) to permit of such' movement. The bar. 91

may. be retained in its raised position whereits loweredge clears the panel QObyjtightening thei winginuts.

In orderto prevent the feelerswitcli' "from actuating the motorto-cause'the' lifting of, the platformiduringthe loadingof the casingand.

until such time'as its automatic action isdesired a. cut" outiswitch' 95" is provided which may. be spring actuated to normally close the circuitto one ofcontact's S'Q' and arranged to open such cir cult when depressed. The switch is mounted in a conven'lentposition on theup'per end of'the' casingan'd'arrangedto, be actuated by a cen-v trai tongue 95 on the cross bar 92i'when'the lat;- ter is'heldin its raised position. With the cross bar-92 in its lower or looking position with respect to panelsection 99', tongue 96 is free of contact with switch 95 which isv then in closed position and control of the operationis determined bythe feeler switch 11. When however the bar is raised and the wing nuts'tightened to hold it in raised position permitting the removal and replacement of the panel, the tongue 98 actuates switch 95 to open position thus disabling control of the motor by the feeler switch. The operator can thm carefully load the casing and make certain that the stringof ammunition is properly arranged and is free to be withdrawn, without having the platform'prematurely lift up toengage the top of the pile with the feeler switch; Upon the completion of the loading and the return of the panel section to close position, the dropping of cross bar 92will cause withdrawal'of the tongue from switch 95" which will thereupon close and irestorecontrol to the feeler switch under the main control of manual switch i602 The lifting of the platform is then under.

the control of the feeler switch which .Will'causeu the motor to lift the pile until the top ofthe pile raises the toe H to thefull lineposition shown in Fig. 4 at which timefurtherraising is;

terminated. It will'b'e understood'that'the bar This section is flanged It is locked.

92 may be lowered to effect closing of switch 95 even with panel 9!! removed, if a raising of the platform is desired under those conditions.

A control switch box we is provided in a suitable location, preferably mounted at the upper end of the casing and comprises the manual control mechanism for reversing the operation of the motor when it is desired to lower the platform in the course of loading additional ammunition thereon. While the switch box H10 may contain a single composite switch, for purposes of simplicity it is shown as comprising two separate switches mechanically connected for simultaneous actuation, one being double pole and the other single pole, both being double throw. Thus a, single pole switch IEH provides for selecting either the upper limit switch 35 or the lower limit switch 36. The double pole switch 402 reverses the motor circuit. Preferably the switch combination thus provided is normally biased to the position where the raising circuit of the motor is closed, and is adapted to be placed in the opposite or lowering position in response to manual operation. A suitable arrangement for this purpose is to spring bias the two switches into the raising position. The switch assembly may if desired be arranged to also remain in the lowering position.

Referring to the circuit diagram it will be observed that when the switch H39 occupies the lowering position, the circuit is from L+, switch I91, lower limit switch 36, switch i2, the armature 2%. of the motor, switch 52, the field 291) of the motor, the magnetic brake 32 to the grounded negative. The lowering of the platform is thus under the control of the manual switch I until the lower limit of the platform is reached when it stops.

When the manual switch is in the raising position, the circuit is from L+, switch i DI, top limit switch 35, one side of disconnect plug 8%, socket 82, feeler switch ll, back through the disconnect plug and socket, interlock switch 95, switch I02, through the motor armature 29a in the opposite direction, the motor field 291) and the magnetic brake .32 to the negative ground, to give reverse operation. Operation is then under the joint control of manual switch lfifi, feeler switch TI and the interlock switch 95 until the upper limit is reached when the motor stops.

In operation, with the platform loaded the upper level of the string of ammunition is as shown in Fig. 4, and such as to raise the feeler shoe Ill to its upper position, opening switch fl and terminating further lifting movement of the platform. Under the operation of the gun, the string of ammunition is drawn upwardly thereby, resulting first in the withdrawal of the topmost layer of ammunition and allowing the feeler ishoe T0 to drop to the level indicated by the second layer of ammunition in Fig. 4. However this movement is insufficient to cause the trippin of switch Ti, and the level of the platform remains the same until the string has been drawn far enough to remove the first several shells of the second layer from beneath the toe H of the feeler device. At this time the feeler shoe drops into the dotted line position of Fig. 4 at which time it rests upon the third layer of ammunition. As it drops into this lower position, switch Ti is tripped and thus completes the circuit for the raising operation of the motor, the motor commencing to operate and lifting the platform with the ammunition thereon. Such lifting continues until the ammunition arrives at the upper level where the shoe occupies its full line posi'- tion, at which point switch 1'! is opened and further lifting ceases. Even should the operation of the gun have ended immediately following th closing of this circuit, it will be clear that the top layer of ammunition occupies the recess beneath bracket BE! and does not contact or inter-- fore with the switch mechanism.

Such lifting operation continues intermittently as the ammunition is used and under control of feeler switch it until the platform reaches its uppermost position where it engages upper limit switch 35, tripping the same to open position and deenergizing the motor.

In order to return the platform to its lower position, manual switch I6 is thrown to its reverse position, thereby disconnecting the feed switch l! and directly connecting the motor in the reverse operating direction. Operation continues in this direction as long as the switch is held in reverse position, the platform moving downwardly as far as desired, and being stopped only when it reaches the lower limit of its travel by the opening of lower limit switch 36 or by release of the switch assembly 596. It will be noted that the lowering circuit does not include any of the mechanism carried by the feed tray and hence it is possible to operate the platform to lower the same while the tray is removed from the top of the casing, the operation in this respect being different from that for the raising operation.

If-he invention thus provides an ammunition feeding device for supplying a string of ammunition to a gun while maintaining the same at a substantially uniform level, entirely automatic and without the necessity of the operator operating the control. The gun action is thus facilitated and made more certain, and the entire arrangement is protected and assurance provided against accidental operation which might result in damage or injury to the operator.-

The entire structure throughout is arranged so that the elements can be assembled to provide for right or lefthand feeding, all structures being reversible so that two assemblies can thus be made. Such flexibility of arrangement is particularly desirable where it is desired to establish repair stations for aircraft gun turrets for example, the interchangeability of the ammunition feeder parts of this invention greatly facilitating and simplifying the number of parts required.

The invention has been described with reference to the feeding of ammunition to an automatic gun, by way of specific example, but is also applicable for the regulated supply and feeding of other articles where similar or analogous conditions are encountered.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

l. A feeding device for an automatic gun utilizing a string of ammunition comprising a casing adapted to be mounted in fixed relation with respect to the gun and to receive the string of ammunition in a series of layers, said casing having a delivery passage for said string of ammunition through the top and adjacent one side thereof, a platform for supporting said layers of a mmunition, poweractuated means for lifting said plat form, and control means responsive to the level of the top layer and located in spaced relation with said one side of said casing and out of the path .of travel of said string of ammunition for rendering said mechanism'successively operative and inoperative as the ammunition is withdrawn from said casing through said passage to maintain the top layer of said ammunition within predetermined limi s of level.

2. A feeding device for an automatic gun utilizing a continuous string of ammunition comprising a casing adapted to be mounted in fixed relation with respect to the gun and to receive the string of ammunition in a series of layers, said casing having a delivery passage for said string of ammunition through the top and adjacent one side thereof, a platform for suppor ing said layers of ammunition, power actuated mechanism for lifting said platform, and control means for rendering said mechanism operable intermittently as the ammunition is withdrawn from said casing, said control means including a feeler device located at the opposite side of said casing out of the path of travel of said string of ammunition and responsive to the level of the upper layer of ammunition in said casing to maintain said layer within predetermined limits of level.

3. A feeding device of the character described for feeding a continuou s ring of articles comprising a casing adapted to receive the string of articles in a series of layers, a platform within said casing for supporting said layers of articles, a feed table su ported at the top of said casing over which said string of articles is fed upon withdrawal from said casing, a feeler device carried by said feed table and adapted to extend into said casing adjacent the upper end thereof for sensing the level of the top layer of said articles, and power actuated means operated under control of said feeler device for maintaining said top layer of articles at a predetermined level adjacent said feed table.

4. A feeding device of the character described for feeding a string of articles com rising a casing adapted to receive the string of articles in a series of layers. a platform within said'casing for suppor ing said layers of articles, a feed table removably supported at the top of said casing over which said string of articles is fed upon withdrawal from the casing, a vfeeler device carried by said feed table and extend n into the upper end of said casing for sensing the level of the top layer of said articl s, power actuated means operated under control of said feeler device for lifting said platform to maintain said top layer of articles at a predetermined level, and means for disabling control of said power actuated means by said feeler device upon removal of said feed table from said casing.

A feeding device of the character described for supplying a string of articles comprising a casing to receive the string of articles in a series of layers, a platform within said c sin for sup-. porting said layers of articles, a feeler device ex.- tending into the upoer end of said casing for sensing the level of the top layer of s id articles, power actuated means operated under control of Said feeler device for lifting said platform to maintain said top layer of articl s at a predetermined level, and means for disablin control of said power actuated means by said feeler device during the loading of articles into sa d casing upon removal of said feed table from said casing.

6. A feeding device of the character described for feeding a string of articles comprising a casing adapted to receive the string of articles in a series of layers, a removable cover member on said casing providing access to the interior of said casing, a platform within said casing for supporting said layers of articles, a feeler device extending into the upper end of said casing for sensing the level of the top layer of said articles, power actuated means operated under control of said feeler device for lifting said platform to maintain said top layer of articles at a predetermined level, and means for disabling control of said power actuated means by said feeler device upon removal of said cover member from said casing.

7. A feeding device of the character described for feeding a string of articles comprising a casing adapted to receive the string of articles in a series of layers, a removable cover member on said casing providing access to the interior of said casing, a platform within said casing for supporting said layers of articles, a feeler device extending ino the upper end of said casing for sensing the level of the top layer of said articles, power actuated means operated under control of said feeler device for lifting said platform to maintain said top layer of articles at a predetermined level, means for disabling control of said power actuated means by said feeler device upon removal of said cover member from said casing, and manually actuated means operable when said cover member is removed for restoring control of the lifting of said platform to said feeler device.

8. A feeding device of the charac er described for feeding a string of articles comprising a casing adapted to receive the string of articles in a series of layers, a platform within said casing for supporting said layers of articles, a cross arm movable upon said casing, a flexible cable attached to said platform and to said cross arm for causing the raising and lowering of said platform in response to the opposte movement of said cross arm, a motor mounted on said casing, driving connections between said motor and said cross arm to cause operation of said cross arm and resul ing travel of said platform, limit switches adapted to be positioned on said casing in side by side relation to each other, and means carried by said cross arm and said plat orm respectively for actuating said limit switches selectively upon the movement of said platform to the upper and lower limits of its travel.

9. A feeding device of the character described for feeding a string of articles comprising a casing adapted to receive the string of articles in a series of layers, a platform for supporting said layers of articles, motor means for raising and lowering said platform, means responsive to the level of the articles in said casing for controlling said motor means to maintain a constant level of the upper surface thereof, and additional means for counterbalancing th wei ht of the articles on said platform with a force varying pro ressively with the quantity of articles on said platform.

10. A feeding device of the character described for feeding a string of articles comprising 9, casing ada ted to receive the string of articles in a series of layers, a platform for supporting said layers of articles, motor means for raising and lowering said platform, means responsive to the level of the articles in said casing for controlling said motor means to maintain a constant level of the upper surface thereof, and means separate from said mo or means for developing a variable counterbalancing action on said platform de- 11 creasing in amount upon reduction of the weight of articles remaining on said platform.

11. A feeding device for an automatic gun utilizing a string of ammunition comprising a casing adapted to be mounted in fixed relation with respect to the gun and to receive the string of ammunition in a series of layers, a platform within said casing for supporting said layers of ammunition, power actuated means for raising and lowering said platform, control means for said power actuated means responsive to the upper level of said articles in said casing to maintain a substantially uniform level thereof, and resilient means for counterbalancing the weight of said ammunition on said platform with a force Varying directly with the quantity of ammunition on said platform.

12. A feeding device for an automatic gun utilizing a string of ammunition comprising a casing adapted to be mounted in fixed relation with respect to the gun and to receive the string of ammunition in a series of layers, a platform within said casing for supporting said layers of ammunition, a feed table supported at the top of said casing over which said string of ammunition is fed to the gun, a feeler device carried by said feed table and projecting into said casing for sensing the level of the top layer of said ammunition, flexible cables on said casing for supporting and lifting said platform, a motor supported on said casing and connected to said cables to effect raising and lowering of said platform, and means for controlling the operation of said motor in response to the position of said feeler device to maintain said top layer at a predetermined level.

13. A feeding device for an automatic gun utilizing a string of ammunition comprising a casing adapted to be mounted in fixed relation with respect to the gun and to receive the string of ammunition in a series of layers, a platform within said casing for supporting said layers of ammunition, a feed table supported at the top of said casing over which said string of ammunition is fed to the gun, a feeler device carried by said feed table and projecting into said casing for sensing the level of the top layer of said ammunition, flexible cables on said casing for supporting and lifting said platform, a motor supported by said casing and connected with said cables to effect raising and lowering of said platform, means for controlling the operation of said motor in response to the position of said feeler device, and means for terminating further operation of said motor when said platform reaches upper and lower limits of its travel.

14. A feeding device for an automatic gun utilizing a string of ammunition comprising a casing adapted to be mounted in fixed relation with respect to the gun and to receive the string of ammunition in a series of layers, a platform within said casing for supporting said layers of ammunition, a feed table supported at the top of said casing over which said string of ammunition is fed to the gun, a, motor operatively connected with said platform for raising and lowering the same, a feeler device for sensing the level of the top layer of said ammunition means for controlling said motor in response to said feeler device to maintain the top layer of said ammunition at a predetermined level, and a manual reversing switch normally biased to position to control said motor to effect the raising of said platform and adapted upon manual operation to reverse the operation of said motor to effect the lowering of said platform.

15. A feeding device for an automatic gun utilizing a string of ammunition comprising a casing adapted to be mounted in fixed relation with respect to the gun and to receive the string of ammunition in a series of layers, a platform within said casing for supporting said layers of ammunition, a feed table supported at the top of said casing over which the string of ammunition is fed to the gun from one side of said casing, a feeler device carried by said feed table and projecting into the casing adjacent the other side thereof for sensing the level of the top layer of said string as said top layer is first removed from beneath said feeler device, and power actuated means operated under control of said feeler device for maintaining said top layer at a predetermined level.

16. A feeding device of the character described for feeding a string of articles comprising a casing adapted to receive the string of articles in layers, a platform within said casing for supporting said layers of articles, a motor operatively connected with said platform for raising and lowering the same, a feeler device for sensing the level of the top layer of said articles and controlling the operation of said motor in response thereto to maintain a predetermined level thereof, and a manual reversing switch normally biased to position to effect the raising of said platform and adapted upon manual operation to reverse the operation of said motor to effect the lowering of said platform.

17. A feeding device of the character described for feeding a string of articles comprising a casing adapted to receive the articles in a series of layers, a platform within said casing for supporting said layers of articles, a, feed table supported on said casing over which the string of articles is fed from the top and adjacent one side of the casing, a feeler device projecting into the casing adjacent the other side thereof and out of the path of movement of the string of articles for sensin the level of the top layer of said string as said top layer is first withdrawn from beneath said feeler device, and power actuated means operated under control of said feeler device for maintaining said top layer at a predetermined level.

JOHN D. SASSER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 441,673 Krnka n- Dec. 2, 1890 789,142 Chichesfier May 9, 1905 864,132 Hood Aug. 20, 1907 1,412,287 Kovalefi' Apr. 11, 1922 1,708,621 Harvey Apr. 9, 1929 1,977,008 Neher Oct. 16, 1934 1,996,618 Huber Apr. 2, 1935 1,998,317 Harvey Apr. 16, 1935 2,076,186 Reynolds Apr. 6, 1937 2,117,396 Birr May 17, 1938 2,186,478 Dehuif Jan. 9, 1940 2,3141004 Marschke Mar. 16, 1943 2,358,319 Dupee Sept. 19, 1944 FOREIGN PATENTS Number Country Date 4 9,943 Great Britain July 7, 1936 

